Thermal shock caused by the injection of molten material, such as aluminum, into a casting die may lead to an early failure of the die. The thermal shock is a result of an extremely rapid change of temperature due to the high temperature of the molten material. A hydraulic press is used to exert pressure on the die in order to keep the die closed during the injection process. Typically, the failure occurs in the entrance or gate area of the die. After repeated injection, cracks begin to form in the surface of the die in the impact area. For example, cracks caused by thermal stress originate at the surface of the die, and gradually progress into the substrate until failure of the die occurs.
As subsequent parts are formed in the die, molten aluminum may fill the cracks during the injection process. When the molten aluminum solidifies to form the part, the part may adhere within the cracks. Therefore, the part may be damaged upon removal from the die. Additionally, excess aluminum may be retained in the die, further hindering subsequent part formation.